The present invention concerns a lock device for use in connection with elongated surgical instruments such as surgical needles, electrodes, catheters, endoscopic equipment, etc.
In neurosurgical operations, for example, instruments are commonly inserted into the brain. These instruments must be positioned in a highly controlled manner with regard to adjustment of both angle and depth.
On the subject of angular orientation of surgical instruments we refer to the applicant""s U.S. Pat. No. 6,328,748 which is hereby included as a reference in its entirety. This patent describes a holder for stereotactic equipment. The said holder is based on the use of a ball joint which permits angular adjustment of equipment. The ball has a channel through which the equipment is passed.
Several known locks are based on securing the instruments at a specific depth by placing a screw in between the instrument and a collar around it. Screw locks of this kind lead to great pressure over a small area on the instrument. If the instrument is a surgical needle, this can cause damage to the needle, which is hollow and therefore not particularly resistant to local pressure on the wall.
The lock which is employed here is a collar lock consisting of a round plate with two halves connected together in a joint and a screw which permit the parts to be separated from each other or to be joined together. When the parts are joined together, they are pressed together uniformly round the entire periphery of the instrument which is thereby locked to the collar in a particular position.
When the instrument is positioned in the operative field in, e.g., the brain, it may be desirable to move it in the longitudinal direction. This movement must be controlled and as precise as possible.
U.S. Pat. No. 5,056,523 describes a stereotactic frame system for positioning a probe tip relative to a target area in the body. The frame""s co-ordinates for biopsy taking are set directly by looking at the area on an X-ray. A biopsy needle is attached to the frame by means of a screw lock. The needle is supported by an adaptor which passes down into an adaptor holder. The needle is further supported and passed through a plate with several holes. The single lock which is employed is not sufficient to provide accurate positioning and movement of the needle in the depth direction relative to the frame.
U.S. Pat. No. 5,643,286 discloses a microdrive for use in stereotactic surgery. This device comprises an external guiding frame, a stop element equipped with a ruler for measurement of distance, and an instrument holding element. When in use, the instrument will be guided by means of the frame, and the distance between the stop element and the instrument holding element will be read on the ruler. The device according to U.S. Pat. No. 5,643,286 comprises an external frame, which requires a lot of space, projects from the operative field, and includes several small parts.
There are many situations where it is desirable to enter the brain from below. In this case the ends of the various surgical instruments will be facing shoulders and neck. The instrument described in U.S. Pat. No. 5,643,286 will then come into conflict with these anatomical structures. For this reason it is important that the guiding arrangement for the instrument should not occupy more space than is absolutely necessary. The frame in U.S. Pat. No. 5,643,286 projects a long way out from the operative field, and this is disadvantageous since there is a greater possibility of brushing against the equipment by mistake. Such accidents can also cause significant damage. Moreover, the length of the frame is fixed, independent of the distance one wishes to measure. When small movements are carried out within the brain, the frame is unnecessarily large, which may lead to the above-mentioned disadvantages. In addition to this the frame restricts movement of the instrument in the longitudinal direction. The device cannot be used in connection with short needles, which are used for procedures in the shoulder and neck area. It is intended for use together with a stereotactic frame. When it is used in biopsy taking the above-mentioned device will be attached to a biopsy needle, where the needle""s two upper parts must be capable of rotating freely and independently of each other for sampling. This is not possible when using this device. The device according to U.S. Pat. No. 5,643,286 also includes several parts which have to co-operate with a high degree of precision, and which have to be disinfected after use. This entails high production costs and considerable time consumption. The equipment cannot be used in several locations during the same operation without re-sterilisation.
The above-mentioned problems in the known devices have been solved by means of the lock device according to the present invention. This consists of at least a first and a second distance member and a stop member, where all parts are movable in the longitudinal direction relative to the instrument and thereby relative to one another, and are individually lockable in the depth position relative to the instrument. The lock device is characterized in that the distance members and the stop member surround the surgical instrument, which thereby forms a guiding frame for the said parts, and that integrated in the distance members there are indication devices for indicating the position of the members relative to each other.